1. Field of the Invention
The present invention relates to an ink jet printer, and, more particularly, to a method of performing printhead maintenance in an ink jet printer.
2. Description of the Related Art
Ink jet printers typically employ a reciprocating carriage supporting one or more printheads. The printheads are capped in a maintenance station when not in use. If the printheads are used frequently, ink is being fired through the nozzles at a rate such that the ink will not clog up and harden over time, or grow crystals in the ink. If the printheads are not used frequently, the long-term inactive period allows the nozzles to clog due to evaporation, ink crystal growth, and/or settling of the ink particles. The nozzle clogs diminish print quality, and depending on the period of time, can cause the printhead to fail beyond recovery. In addition, the use of pigment inks can accelerate the failure of nozzles due to clogs.
Printhead maintenance requires periodic jetting, sometimes called spitting, of ink droplets to clear contamination from nozzles or to ensure proper ink chemistry at the nozzle openings. The droplets are frequently collected in a waste ink reservoir called a spittoon. This ink droplet firing, as a part of a maintenance algorithm, occurs to clear the printhead nozzles of contamination or to prevent ink chemistry changes at the nozzle openings due to crusting, viscosity changes, or separation of ink constituents. For example, during printhead spit maintenance, the printhead may be moved by the carrier to a fixed location, and the printhead fires into the fixed location. The fixed location may be, for example, an open waste ink reservoir, a waste ink collection surface, or a foam filled spit tower, positioned outside the print zone of the printer.
A known method of initiating a printhead maintenance routine is to monitor printhead usage, e.g., the number of times that the nozzle heaters are fired. When the printhead usage reaches a predetermined threshold level, the printhead maintenance routine is initiated. This method of initiating printhead maintenance is effective, but may be computationally expensive and requires memory to monitor printhead usage on a total or per nozzle heater basis.